The edges aren't dark enough
The first thing I noticed when I looked at your blend document is that the mesh for your shoe is reversed. If you go into edit mode, select all vertices, and select "Recalculate" from the "Shading/UVs" menu, they should face back the right way. You need to do this for the solution to work. 

First, add a "MixRGB" node to your material, as well as two "RGB" nodes and a "Fresnel" node. Connect each "RGB" node to one of the inputs of your "MixRGB" node, and attach the "Fresnel" node to the "Fac" input of the "MixRGB" node. The layout should look like this:

Next, connect the "Color" output of the "MixRGB" node to your "Diffuse" shader. Now, whichever "RGB" node you connected to the bottom of the "MixRGB" node becomes the edge color, and the top "RGB" node becomes the inside color. The final material layout should look like this: 

To show that this works, I set the outside color to red, and the inside to green, and this is the result: 

Of course, for your case, you can set the inside color to a light brown, and the outside to a darker brown. I hope this helped! Happy Blendering!
Cheers,
Graves Broderick